The present invention relates generally to a conductive fabric and, more particularly, to a conductive wrist band employing such conductive fabric.
When handling static sensitive electronic components, such as integrated circuits and the like, there is a problem of damaging such components due to static electricity. One method of grounding such static electric charges has been to provide a conductive wrist strap about the wrist of the individual handling such components, which is in contact with the skin and is connected to ground by a wire connected to the wrist strap. As a result, the electrostatic charge accumulation on the individual is dissipated and the accumulation of additional electrostatic charge is prevented. Such conductive wrist straps are also provided in situations where the individual can be hurt, for example, in the proximity of an explosive or hazardous environment.
Some wrist bands are comprised of an extruded or fabric base matrix with a conductive plastic or film sewn into the structure. The conductive layer contacts the skin, and a metal snap connects the band to a ground cord that dissipates static electricity built-up. Conventionally, these wrist bands use Velcro fasteners to secure the band to the wrist and are therefore stiff and uncomfortable. The same disadvantage generally results from metallic wrist bands, such as disclosed in U.S. Pat. Nos. 4,373,175 and 4,459,633. These latter devices also provide the disadvantage that the metallic material exists on the exterior surface thereof, and is therefore exposed to the electronic component or hazardous materials.
In order to make such wrist bands more comfortable for the user, it has been proposed in U.S. Pat. Nos. 4,398,277 and 4,475,141 to manufacture the conductive wrist bands from a fabric material.
In U.S. Pat. No. 4,475,141, the wrist band is made of an elastomeric fabric having a conductive thread stitched therein in a zig-zag manner. However, the conductive thread extends to the outer surface of the wrist band, whereby electrostatic charges may be transferred to the sensitive electronic components or harzardous materials.
U.S. Pat. No. 4,398,277 is an improvement thereover, since the conductive yarn is woven on one side only of the wrist band, while an insulative yarn is woven into the other side of the wrist band and in an interconnecting manner with the conductive yarn. Thus, the conductive yarn does not extend to the exterior surface of the wrist band. However, with this patent, the electrically conductive yarn is plaited with an elastic fiber. In addition, the insulative yarn contains an end having an insulative fiber plaited with an end having an elastomeric fiber. Because an elastomeric fiber is plaited with each of the insulative fiber and the conductive fiber, it is not easily handled in fabricating the wrist band because of the elastic nature of both yarns. Further, because the conductive yarn is plaited with an elastomeric fiber, the elastomeric fiber is in contact with the skin and may provide irritation thereof. Another problem with such arrangement is that the elastomeric fibers tend to close the fabric structure, thereby providing less aeration for the user. This latter problem is further enhanced by the fact that there are two distinct layers, one on top of each other, providing a double thickness, which is less comfortable and provides less aeration.